When using a dry film photopolymer resist material, such as that manufactured by E. I. du Pont de Nemours and Company, Inc. and sold under the trademark RISTON.RTM., it is necessary to laminate a layer of that material onto the surface of a circuit board or other substrate prefatory to exposure by actinic radiation. Typically, the layer of photopolymer resist material is laid over the surface of the substrate to be covered and the substrate and resist passed between the nip of heated laminating rolls. The surface of the substrate may be previously scrubbed to remove oxide layers and other contaminants therefrom. The scrubbing assists in the adhesion of the resist material to the substrate. If done manually, the preparation of the substrate and the introduction and removal thereof into and from the laminating rolls is time consuming and expensive.
It is advantageous to increase the throughput of the laminating operation by providing an apparatus adapted to automatically prepare the surface of the substrate, convey the prepared substrate to the lamination region which contains the heated laminating rolls, and thereafter remove laminated boards from the apparatus for further fabrication. However, in any automated apparatus certain minimum requirements are believed necessary in order to most efficiently and effectively laminate a resist layer to the surface of a substrate.
For example, if copper coated boards are to be laminated with a resist material, it is believed to be advantageous to utilize a conveyance arrangement which expeditiously translates the board from the region in which the surface thereof is scrubbed to the region in which the board is laminated in order to minimize the oxidation of the surface of the substrate to the fullest extent possible.
To avoid wastage of resist material, it is also desirable that individual boards be presented to the laminating rolls with as little a gap as possible between a given board and a trailing board. Thus, any conveyance arrangement should be adapted to avoid cumulative gapping between successive boards introduced into the lamination region. It is believed to be most desirable to provide a conveyance arrangement wherein successive boards are in an abutted relationship (tail-to-head) at the time one of the boards is introduced into the laminating rolls. Moreover, any conveyance arrangement should be able to maintain abutment between successive boards without regard to variations in board length from run to run. Since the boards being laminated are relatively thin planar members, it is also necessary that any conveyance arrangement be adapted to prevent board overlap. That is, the leading edge of a trailing board must not extend over or under the trailing edge of a leading board. Such an occurrence can potentially render inutile both boards.
In the lamination region itself, it is believed desirable to provide a mechanism whereby the laminating rolls are accurately brought into contact with the leading edge of a leading board in a run and (assuming the boards are butted) removed from contact as the trailing edge of the last trailing board exits the laminating rolls. Such a practice is advantageous in that it avoids wastage of resist material. Moreover, the laminating rolls should be susceptible to accurate opening and closing motions which would bring the rollers into contact with the surfaces of the board and predictably impart a predetermined pressure force to the board to laminate the resist layer thereto. The gap, or nip, formed between the rollers when the rollers are closed should, moreover, be predictably adjustable.
Once the board and resist material have been laminated, the laminate (i.e., substrate and resist layer adhered thereto) so formed should be automatically removable from the apparatus. With those resist materials which are provided with a backing strip the laminate may be moved through the apparatus incidentally to the take-up of the backing strip. When the backing strip is being taken-up, care must be exercised that proper tension is maintained on the strip. It is therefore believed advantageous to provide a slip clutch tension device to insure that the take-up tension force exerted by a take-up roller on the backing strip be held within appropriate limits.
While any portion of the laminate is still within the apparatus the laminate is subjected to a restraining force which tends to resist any displacing force imposed on the laminate to assist in its withdrawal from the apparatus. However, when laminate is drawn through the automated apparatus it is desirable to provide a structural arrangement whereby the laminate is separated from the backing strip and any unadhered resist present between the trailing edge of the laminate and the leading edge of the next-successive laminate. Accordingly, it is believed advantageous to provide a gripping arrangement adapted to grasp the laminate when a predetermined portion thereof has exited from the apparatus and to exert a force on the laminate which pulls it free from the trailing resist material when the backing strip is completely removed from the laminate.